Changes in energy status of leaf cells as a consequence of mitochondrial genome rearrangement

The MSC16 cucumber (Cucumis sativus L.) mutant with lower activity of mitochondrial Complex I was used to study the influence of mitochondrial metabolism on whole cell energy and redox state. Mutant plants had lower content of adenylates and NADP(H) whereas the NAD(H) pool was similar as in wild type. Subcellular compartmentation of adenylates and pyridine nucleotides were studied using the method of rapid fractionation of protoplasts. The data obtained demonstrate that dysfunction of mitochondrial respiratory chain decreased the chloroplastic ATP pool. No differences in NAD(H) pools in subcellular fractions of mutated plants were observed; however, the cytosolic fraction was highly reduced whereas the mitochondrial fraction was more oxidized in MSC16, as compared to WTc. The NADP(H) pool in MSC16 protoplasts was greatly decreased and the chloroplastic NADP(H) pool was more reduced, whereas the extrachloroplastic pool was much more oxidized, than in WTc protoplast. Changes in nucleotides distribution in cucumber MSC16 mutant were compared to changes found in tobacco (Nicotiana sylvestris) CMS II mitochondrial mutant. In contrast to MSC16 cucumber, the content of adenylates in tobacco mutant was much higher than in tobacco wild type. The differences were more pronounced in leaf tissue collected after darkness than in the middle of the photoperiod. Results obtained after tobacco protoplast fractionating showed that the increase in CMS II adenylate content was mainly due to a higher level in extrachloroplast fraction. Both mutations have a negative effect on plant growth through perturbation of chloroplast/mitochondrial interactions.